| 其他摘要 | Revegetation is one of the most effective methods for increasing soil organic carbon
(SOC), improving the stability of soil aggregates, and changing the composition of organic
carbon on the Loess plateau in China. During the process of vegetation restoration,
understanding the composition of the SOC functional groups, which is important to deepen
our understanding of SOC learning stability mechanism. This study directly measured the
distributions and composition of SOC functional groups from different revegetation ways
using XANES and SR-FTIR Spectroscopy. This study provides the first detailed investigation
of changes in SOC functional groups composition in different size aggregates during
vegetation restoration process on the Loess Plateau. This may provide fresh insights into the
effects of natural vegetation restoration on the chemical stability of SOC. The main results
and conclusions were presented as follows:
1. Vegetation restoration in semi-arid nature grassland changed the content of functional
group and distribution of SOC in different soil layers, and prompted structural stability of
SOC in the process of the grassland recovery. Peak intensity of aliphatic-C from fallowing
grasslands significantly increased with increasing years of fallowing. Results obtained by
SR-FTIR technique were analyzed which showed that compared with slop farmland, relative
content of functional groups from fallowing grasslands SOC were increased, the growing rate
of aliphatic-C , alcohols-C in 0-5cm , 10-20cm soil horizon was greater than growing rate
aromatic-C. Results obtained by soft X-ray technique are consistent with SR-FTIR, and
relative content of the same functional groups(aliphatic-C, aromatic-C) gained by two
determination methods were T-test, which was not significant (P > 0.05), indicated that using
Synchrotron radiation soft X-ray for the determination of SOC structural change of fallowing
grasslands is feasible.
2. Planting alfalfa for long time increased SOC, improved stability of aggregates, changed the distribution and content of SOC functional groups in soil and different size aggregates.
The improvement effect was in 8 years. Percentage of > 0.25 mm aggregates increased with
the increasing of planting years. Relative content of saturated alkyl increased, and which were
fixed mainly in 0.25-1 mm aggregates. Relative content of aliphatic-C and alcohol-C
decreased with increasing of aggregate sizes. The increasing of the aliphatic-C and alcohol-C
existed major in macro-aggregates, while, aromatic-C distributed in < 0.25 mm aggregates.
The change content of functional groups in macro-aggregates were more clear than <0.25mm
aggregates, which showed that organic carbon stability of micro-aggregates was higher than
macro-aggregates, increasing of labile functional groups (aliphatic -C, alcohol-C) of SOC
were easier than aromatic-C in the process of plating. Percentage ratio of aliphatic -C,
alcohol-C, and saturated alkyl of SOC are main, and the change of those are most active, so
that increasing of aliphatic -C, alcohol-C and saturated alkyl contributed immense to the
increasing of SOC.
3. Plant succession improved chemical stability of SOC, which indicated that revegetation
can promote increases in aliphatic-C and ketone-C contents in both the 0-5 cm and 20-40 cm
soil layers, and this effect gradually increased with plant succession. Labile oxidation
functional groups of SOC (alcohol-C, polysaccharide-C, telescopic vibration aliphatic-C)
increased significantly, recalcitrant ones (deformation vibration aliphatic-C, and aromatic-C)
also increased during plant succession promoting SOC increase process. Especially,
functional groups of SOC increased obviously in Sophora viciifolia, Quercus liaotungensis
stages, the vegetation restoration improve the chemical stability of SOC. Plant succession
effected more the change of SOC from 0-5 cm soil layer than 20-40cm layer.
4. The result showed that polysaccharide-C was the most abundant in the 0.5-0.25 mm
aggregate, while carbonyl-C was found mainly in the <0.25 mm aggregate. High levels of
aliphatic-C, carboxylic-C and alcohol-C were found mainly in the 5-2 mm, 0.5-0.25 mm, and
<0.25 mm aggregations, respectively. In forest aromatic-C was mainly in <0.5mm aggregate,
and absolute content of aromatic-C from forest increased obviously in different aggregates.
5. The type of functional groups of SOC(polysaccharide-C, aliphatic-C, aromatic-C,
alcohol-C) from semi-arid nature grassland and semi-humid grassland grassland was the same,
moreover, which from planting alfalfa land included -COOH, alkane .In three grassland, the
result showed that aliphatic-C , alcohols-C, polysaccharide-C increased significantly during
the vegetation restoration process，aromatic-C perform the trend of increasing. Results
obtained by SR-FTIR technique were semiquantitative analyzed which showed that the rate
increasing of aromatic-C from the yunwu mountains grassland>Ziwuling grassland > alfalfa
land. It illustrated that structural stability of SOC enhance more in yunwu mountains
grassland than Ziwuling grassland and alfalfa land.
Key Words： the vegetation restoration process，aromatic-C perform the trend of increasing. Results
obtained by SR-FTIR technique were semiquantitative analyzed which showed that the rate
increasing of aromatic-C from the yunwu mountains grassland>Ziwuling grassland > alfalfa
land. It illustrated that structural stability of SOC enhance more in yunwu mountains
grassland than Ziwuling grassland and alfalfa land.
Key Words：Revegetation, Soil organic carbon functional groups, Aggregates, XANES,
SR-FTIR |
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